If interstellar travel is possible for living creatures at all, they might originate from carbon planets or other habitats where life would evolve a slow perception of time.
It’s very difficult to imagine biological beings such as humans ever traveling to other star systems. Even if we achieve a significant fraction of the speed of light, for example, 10%, it would take decades and centuries to reach the nearest exoplanets. With advances in artificial intelligence and robotics, we might send automated missions to such destinations. They could perform just as well as we do and send back footage from the surfaces of exoplanets. Without biological needs, they can spend decades and centuries in spaceships.
Stars within galaxies have varied velocities and directions of movement, and sometimes they approach each other. This provides a chance of interstellar travel for biological creatures. Our system will be just 0.16 light-years away from Gliese 710 in 1.3 million years.
Finally, the burden of such voyages would be lighter for creatures that perceive time more slowly than humans. If they lived thousands of years and viewed reality more slowly, humans would move around for them as in an accelerated movie. It’s the case with some Earth’s creatures. Flies perceive reality about four times faster than us and can dodge our hand when we try to slap them. On the other hand, we perceive reality about four times faster than turtles, and they move very slowly from our perspective.
The same effect could be even stronger for animal-like organisms, which would evolve on colder worlds where chemical reactions are slower. Some hypothetical biochemistries of life are expected to be like this, such as those involving certain life biochemistry solvents in which chemical reactions would be slower. Hypothetical carbon planets are an example of that. Their liquid oceans could consist of non-polar hydrocarbons, and some of these can be liquid at much lower temperatures, existing on distant orbits of stars where there is less sunlight than on Earth.
Creatures originating from such an environment could have it easier to travel across the universe, perceiving the passage of time more slowly. If we ever met them in person, it could be difficult to distinguish them from plants or elements of scenery because of their slow movement. We would need to communicate with them via artificial intelligence.
Therefore, if galactic empires consisting of many systems exist at all, they might be built by such bizarre creatures. Animals that originated on oxygen-rich planets such as Earth, including humans, are bound to exist in only one system unless biological civilizations eventually transform into an artificial intelligence-based ones, capable of conquering galaxies. They would be much more patient and durable during interstellar travel.